fix: transcription segment dedup, store finalisation, and panel colours

- transcriptionService: track finalizedSegmentCount so only newly-final
  segments are emitted per WS message (was re-processing full array each
  time, causing the live segment to freeze in the completed list)
- transcriptionStore: saveSegment isFinal branch now appends the passed
  text directly instead of currentSegment (currentSegment was stale
  relative to the incoming final)
- CCTranscriptionPanel: record button colour changed from var(--color-text)
  to explicit #2563eb so it is visible in dark mode; completed segment
  backgrounds changed from hardcoded #fff to var(--color-muted) so text
  is readable in both themes; keyword Add button gets same blue fix

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

src/stores/transcriptionStore.ts

@@ -249,11 +249,9 @@ export const useTranscriptionStore = create<TranscriptionState>((set, get) => ({
     const { completedSegments, currentSegment, activeSession, wordCount } = get();
 
     if (isFinal) {
-      // Final segment - move current to completed, clear current
-      const newCompleted = [...completedSegments];
-      if (currentSegment && currentSegment.text.trim()) {
-        newCompleted.push({ ...currentSegment, isFinal: true });
-      }
+      // Final segment — append the finalized text directly (not currentSegment, which
+      // may lag behind or duplicate when WhisperLive re-sends the full segments array).
+      const newCompleted = [...completedSegments, { text, isFinal: true, ...metadata }];
       const newWordCount = newCompleted.reduce(
         (sum, seg) => sum + seg.text.trim().split(/\s+/).filter(Boolean).length,
         0